In logging while drilling and drilling operations, it is necessary to measure information of a drilling trajectory in real time, so that a ground operation engineer can adjust a drilling speed and a drilling direction in real time and complete the drilling operation according to the set well trajectory. In directional drilling in highly-deviated wells, horizontal wells and multilateral wells, it is especially important to measure a well deviation angle, a tool face angle, and an azimuth angle.
The average length of a measuring point of a conventional well deviation angle measurement system is more than 20 meters, which is far away from the bit. Measured information of a stratum is delayed, which is particularly unfavorable to the development of a thin oil reservoir and cannot determine the change of the drilling tool in the oil reservoir. At present, the trend is to install more sensors near the bit, the smaller a distance from the bit is, the more accurate and timely the obtained information of the stratum is.
A well deviation angle measurement principle is obtained according to changes in gravitational components along a well axis and its vertical direction due to different well deviation angles. By installing three orthogonal acceleration sensors along three axial directions X, Y and Z of the drilling tool, the well deviation angle θ can be calculated according to components Ax, Ay and Az of a gravitational acceleration in the axial directions X, Y and Z:
                    θ        =                  arctan          ⁡                      (                                                                                Ax                    2                                    +                                      Ay                    2                                                              Az                        )                                              (        1        )            
A conventional measure while drilling (MWD) technology adopts a static measurement manner, which stops drilling during measurement so as to reduce effects of vibration and impact and the like on the measurement accuracy. Outputs of the acceleration sensors are merely gravitational acceleration signals of the measuring point.Sstate=Sg  (2)
During near-bit dynamic measurement, the outputs of the acceleration sensors not only include a gravitational acceleration, but also include a centrifugal acceleration generated by the rotating of an instrument, and the vibration acceleration and the impact acceleration generated in a drilling process. The outputs of the acceleration sensors during dynamic measurement can be expressed as:Sdynamic=Sg+Sv+Se+Ss  (3)
wherein Sg represents the gravitational acceleration, Sv represents the vibration acceleration, Se represents the centrifugal acceleration, and Ss represents the impact acceleration.
In order to improve the dynamic measurement accuracy of the well deviation angle, it is necessary to remove superimposed components of the vibration acceleration, the impact acceleration and the centrifugal acceleration, and extract components so that the result actually reflects the well deviation angle based on the gravitational acceleration.
There are problems as follows: the conventional measure while drilling (MWD) technology adopts the static measurement manner, which stops drilling during measurement, cannot measure information of the well deviation angle during drilling in real time, is lower in well site operation efficiency since a well trajectory may be obtained by only adopting a manner of fitting measurements of multiple points, and has a difference between the fit well trajectory and an actual drilling trajectory. Meanwhile, MWD is installed within a non-magnetic drill collar on a screw motor, which is away from the bit for about 20 meters, such that the information of the drilling trajectory may not be obtained in real time. During the near-bit dynamic measurement, the effects of the vibration acceleration, the impact acceleration and the centrifugal acceleration on the gravitational acceleration cannot be effectively eliminated.